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- Title
Soil Solution Electrical Conductivity Measurements Using Different Dielectric Techniques.
- Authors
Hamed, Yasser; Persson, Magnus; Berndtsson, Ronny
- Abstract
Accurate measurements of soil solution electrical conductivity (σ[sub w]) are needed in various applications. One recently developed technique that measures σ[sub w] is the Sigma Probe (SP). The SP is supposed to give accurate readings only slightly dependent on water content (θ) and soil type. To test the performance of the SP, it was compared with another dielectric technique, time domain reflectometry (TDR). Both techniques utilize the dielectric constant (K[sub a]) and bulk electrical conductivity (σ[sub a]) to estimate the σ[sub w]. Measurements of σ[sub w] were obtained in a laboratory experiment using nine different soil types with θ in the range 0.05 to 0.50 m³ m[sup -3]. In each soil type, three different σ[sub w] were used (approximately 0.3, 1.2, and 3.0 dS m¹). The linear σ [sub w]-σ[sub a]-θ model used by the SP contains only one soil specific parameter (K[sub 0]). Using this model, the SP readings were constant over the encountered range in θ, whereas the TDR estimation calculated by the same model typically increased at K[sub a] values below the range of 10 to 15. Using the SP with a default K[sub 0] value of 4.1 typically gave a σ[sub w] that was ±20% of the true σ[sub w] when σ[sub w] > 1 dS m[sup -1]. The error in the σ[sub w] estimation for σ[sub w] lower than 1 dS m[sup -1] can be much larger except in sandy soils. The TDR measurements of σ[sub w] using a conventional σ[sub w]-σ[sub a]-θ model were more accurate in all soil types at all θ, with root mean square errors that were lower by about 50% compared with the SP readings. However, this model requires soil specific parameters that have to be obtained during a calibration experiment.
- Subjects
SOIL solutions; ELECTRIC conductivity; DIELECTRIC devices
- Publication
Soil Science Society of America Journal, 2003, Vol 67, Issue 4, p1071
- ISSN
0361-5995
- Publication type
Article
- DOI
10.2136/sssaj2003.1071